A SNP marker for the selection of HfrDrd, a Hessian fly-response gene in wheat
The HfrDrd gene has been reported to be induced specifically in the wheat's defence response to Hessian fly larvae and is not a general stress-responsive gene. The gene is located on chromosome 7DS with a homeologue on 7AS. In this study, two SNPs in the gene that result in amino acid substitutions in the dirigent-like protein have been identified. Both are C/T polymorphisms at nt position 86 and 143 in exon 1 of the gene. The first SNP (from 50 end) causes an alanine-to-valine substitution. The second is a serine-to-leucine change and is located in the conserved dirigent domain. Both 'T' nucleotide SNPs are characteristic of the Hessian fly-resistant genotype, Iris (JX501668, JX501669). Only SNP 143 has been found to be significantly associated with Hessian fly resistance. One hundred and seventy-one Australian cultivars screened were susceptible and have the 'C' nucleotide at SNP 143. The 'T' SNP at nt 143 was found in thirteen resistant cultivars, and the heterozygous state was identified in four other resistant cultivars. This study has identified other resistant genotypes which do not carry the 'T' nucleotide at nt 143 in the gene. Their resistance mechanism possibly involves other Hessian fly-response (Hfr) genes. SNP 143 will be useful for deployment in developing varieties with the resistant HfrDrd allele.